Dual Power Amplifier with Tunable Output Combiner Circuit

This application claims priority under 35 U.S.C. § 119 to European patent application no. 24306890.5, filed 12 Nov. 2024, the contents of which are incorporated by reference herein.

Embodiments of the subject matter described herein relate generally to power amplifiers, and particularly to power amplifiers implemented in cellular base station transmitters.

A cellular base station enables mobile devices to connect with a cellular network. To provide for two-way communications between the mobile devices and the network, a cellular base station may include multiple radio frequency (RF) transceivers, each of which includes a transmitter path (for transmitting signals from the network to the mobile devices) and a receiver path (for receiving signals from the mobile devices and providing the signals to the network).

A transmitter path of a base station transceiver may include several gain stages (e.g., a pre-driver stage, a driver stage, and a final stage). The physical size of the transmitter path is governed, at least in part, by the design of the gain stages and associated circuitry and packaging (e.g., inter-stage isolators, impedance matching circuits, bias circuitry, heat dissipation structures, and so on).

Because cellular base stations typically are deployed in the outside environment, there is a desire to minimize their size in order to make them less conspicuous. Accordingly, cellular communication system operators desire base stations (and thus base station transceivers) that are as small as possible, while still providing excellent performance. Operators specifically desire base station amplifiers that have smaller form factors, flexibility (e.g., designs that can easily be modified for different frequencies of operation), and low cost (e.g., reduced bill of material (BOM)), among other features. With ever present trends toward miniaturization, cost containment, and flexibility, what are needed are more compact cellular base stations, and particularly more compact base station transceivers and base station transmitters.

322 422 522 622 722 383 383 483 483 3 7 FIGS.- 3 7 FIGS.- Embodiments of the inventive subject matter include high performing radio frequency (RF) transmitters (e.g., for cellular base stations or other applications) and, more specifically, RF transmitters that are relatively compact and provide for flexibility (e.g., tunability for different operational frequencies). For example, embodiments of RF amplifiers are illustrated and described herein, which include dual Doherty power amplifiers with output combiner circuits that are integrated (e.g., packaged) in such a manner to provide for compactness, while also providing for frequency tunability. These RF amplifiers enable a cellular communications system operator to utilize the same overall transmitter design (e.g., the same transmitter PCB) for amplifiers that operate in different frequency bands by simply changing, on the transmitter PCB, the packaged RF amplifier device (e.g., device,,,,,) and the value of one or more discrete capacitors (e.g., capacitors,′,,′,), which are accessible outside of the packaged RF amplifier device.

For example, one or more embodiments of RF amplifiers illustrated and described herein include RF amplifier devices that include multiple amplification paths (e.g., multiple amplification paths of a dual Doherty power amplifier) that are integrated into a same discrete package, along with output combiner circuits that combine the amplified output signals from the multiple amplification paths. As will be described in detail later, certain tuning points within the output combiner circuits are accessible outside of the discrete package, which enables additional circuitry (e.g., tuning capacitors) to be electrically coupled to the output combiner circuits. Essentially, the accessible tuning points enable a similar or same packaged RF amplifier device to be utilized in amplifiers that are designed for different operational frequencies. This tunability enables operators to have substantially the same PCB layout (with a different BOM) for amplifiers designed for different operational frequencies.

According to one or more specific embodiments, an RF amplifier may include multiple Doherty power amplifiers, which may be used in a driver amplification stage and, in some embodiments, in a final amplification stage in a transmitter lineup that includes multiple amplification stages. As will be described in more detail later, when a driver amplification stage is implemented with an embodiment of a dual Doherty power amplifier, the RF amplifier may be designed without an inter-stage isolator between the driver and final amplification stages, which presents a further benefit of the inventive embodiments.

100 200 100 100 103 108 1 FIG. 2 FIG. 1 FIG. 1 FIG. Before describing multiple embodiments of RF transmitters and amplifier devices, embodiments of cellular radio systems (e.g., system,) and RF transmitters (e.g., transmitter,) will be described to provide context within a cellular communication system (e.g., within a cellular base station). Specifically,illustrates a cellular radio systemthat may be included in a cellular base station. The cellular radio systemincludes transmitter processing circuitrythat is designed to interoperate with multiple transmitters(several of which are shown enlarged on the right side of), in accordance with an example embodiment.

108 103 108 100 108 Basically, each of the multiple transmittersfunctions to amplify RF signals received from the transmitter processing circuitry, and to provide the amplified RF signals to an antenna (not illustrated) for transmission over the air interface. All of the transmittersin systemmay be designed to operate within a same operational frequency band, or various ones of the transmittersmay be designed to operate within different operational frequency bands.

100 101 102 100 According to one or more embodiments, the cellular radio systemis integrated onto first and second transmitter substrates,(e.g., first and second printed circuit boards (PCBs)), which are physically and electrically coupled together. In one or more alternate embodiments, the cellular radio systemmay be integrated onto a single transmitter substrate.

101 102 101 108 110 101 101 When implemented onto first and second transmitter substrates,, the first transmitter substratemay house various transmit baseband processing circuitry, analog-to-digital converters (ADCs), digital-to-analog converters (DACs), frequency up-converters and down-converters, memory components, some circuitry of the transmitter(e.g., driver amplification stage), and other circuitry. Because the operational frequencies and power levels of this circuitry and components may be relatively low, the performance of the circuitry and components is not highly affected by the materials used for the first transmitter substrate. Accordingly, the first transmitter substratemay be formed from relatively low-cost, low-performance substrate materials (e.g., FR4).

101 110 108 110 110 108 101 190 102 Particular to the inventive embodiments discussed in detail herein, for example, the first transmitter substratemay include one or more driver amplification stagesfor one or more RF transmitters. The driver amplification stagesare designed to operate at relatively low power. The driver amplification stageof each transmitteressentially pre-amplifies an RF transmit signal received from a transmit signal processor on the first transmitter substrate, and provides the amplified transmit signal to a final amplification stageon the second transmitter substrate.

3 7 FIGS.- 110 110 110 101 110 101 110 108 110 110 As will be discussed in detail in conjunction with, each driver amplification stagemay include features that enable the driver amplification stageto be easily “tuned” for high-efficiency operation within a particular operational frequency band, simply by changing one or more discrete components (e.g., discrete capacitors) that are coupled to the driver amplification stageon the first transmitter substrate. This has the advantageous effect of allowing multiple driver amplification stagesto have similar or exactly the same layouts on the first transmitter substrate, even though the driver amplification stagesare coupled to multiple transmittersthat are designed for operation at different operational frequencies. In other words, the layout for multiple driver amplification stagesmay be similar or identical, although different driver stage BOMs may be needed for different operational frequencies. The flexibility of the proposed driver amplification stageis a highly desirable feature for cellular base station operators, and specifically for transmitter designers.

102 101 102 190 108 190 192 102 102 194 190 102 190 2 FIG. The second transmitter substratehouses transmitter circuitry designed for higher-power and/or higher-frequency operation (in comparison to the circuitry housed on the first transmitter substrate). For example, the second transmitter substratemay house a final amplification stageassociated with each transmitter. Although not covered in detail herein, each final amplification stagemay include a high-power amplifier (e.g., a Doherty power amplifier) that is at least partially implemented in a discrete power amplifier devicethat is coupled to the second transmitter substrate. In addition, as will be described in more detail in conjunction with, the second transmitter substratemay house a circulator, which is an RF component that is designed to direct amplified RF signals from the final amplification stageto the antenna (not illustrated), and to direct RF signals received from the antenna to receiver circuitry. Generally, the layout (on substrate) and BOM are different for final amplification stagesthat are designed to operate at different operational frequencies.

190 194 102 102 101 Because the operational frequencies and power levels of the final amplification stageand the circulatormay be relatively high, the performance of these components may be highly affected by the materials used for the second transmitter substrate. Accordingly, the second transmitter substratedesirably is formed from relatively high-cost, high-performance (e.g., low loss) RF substrate materials (e.g., RO4350), which are different from the materials used for the first transmitter substrate. According to some alternate embodiments, as mentioned above, substantially all of the transmitter circuitry may be implemented on a single transmitter substrate, which desirably is formed from high-performance RF substrate materials.

110 110 190 It may be noted here that a conventional transmitter with a driver amplification stage and a final amplification stage typically includes an interstage RF isolator between the driver and final amplification stages. An interstage RF isolator is a relatively high-cost and large component that is designed to protect RF components from excessive signal reflection. In the present context, for example, an interstage RF isolator could be used to protect sensitive RF circuitry on a first transmitter substrate from higher-power RF signal energy generated within a final amplification stage. However, as will be described in detail later, one or more embodiments of driver amplification stagesdiscussed herein are designed to eliminate the need for an interstage RF isolator between the driver and final amplification stages,. This provides the beneficial effect of eliminating the need for a transmitter designer to include the additional cost and space that would otherwise be needed for an interstage RF isolator between driver and final amplification stages of an RF transmitter. Elimination of the inter-stage isolator is possible because, as will be discussed in detail later, embodiments of driver amplification stages discussed herein include two Doherty power amplifiers that are combined in quadrature (e.g., dual Doherty power amplifiers).

2 FIG. 1 FIG. 1 FIG. 1 FIG. 1 FIG. 1 FIG. 200 108 200 203 103 208 294 299 203 208 210 201 101 294 208 290 202 202 is a schematic drawing of an RF transmitter(e.g., any one of transmitters,), in accordance with an example embodiment. The RF transmitterincludes transmitter processing circuitry(e.g., circuitry,), an RF transmitter, a circulator, and an antenna. As mentioned above in conjunction with the description of, according to one or more embodiments, the transmitter processing circuitryand portions of the RF transmitter(e.g., driver amplification stage) may be couped to a first transmitter substrate(e.g., substrate,). Conversely, the circulatorand other portions of the RF transmitter(e.g., final amplification stage) may be coupled to a second transmitter substrate(e.g., substrate,). Alternatively, all of the amplification circuitry of the RF transmitter may be coupled to a single transmitter substrate.

208 108 209 103 203 210 110 310 410 610 710 290 190 209 210 210 290 290 299 294 1 FIG. 1 FIGS. 1 3 4 6 7 FIGS.,,,, and 1 FIG. The RF transmitter(e.g., RF transmitter,) may include, for example, a TX signal processor(e.g., a portion of transmitter processing circuitry(),) and one or more amplification stages, including a driver amplification stage(or “driver amplifier”, e.g., any of amplification stages,,,,,) and a final amplification stage(or “final amplifier”, e.g., final amplification stage,). The transmit signal processoris configured to produce analog transmit signals at RF frequencies, and to provide the transmit signals to the driver amplification stage. The driver amplification stageamplifies the transmit signals by applying a first level of gain, and provides the amplified transmit signals to the final amplification stage, which further amplifies the transmit signals by applying a second level of gain. The final amplification stageprovides the further amplified transmit signals to the antennathrough the circulator.

208 299 294 294 194 295 208 296 299 297 100 297 100 297 1 FIG. In the illustrated embodiment, the RF transmitteris coupled to the antennathrough the circulator. More specifically, the circulator(e.g., circulator,) is a three-port device, with a first portcoupled to the RF transmitter, a second portcoupled to the antenna, and a third port. When the systemis configured to implement Time Division Duplex (TDD) communication for transmit and receive operations, the third portmay be coupled to a receiver (not illustrated). Alternatively, when the systemis configured to implement Frequency Division Duplex (FDD) communication for transmit and receiver operations, the third portmay be coupled to a resistive termination (e.g., a 50 ohm termination, not illustrated).

294 294 295 296 294 295 296 296 297 295 297 297 296 The circulatoris characterized by a signal-conduction directivity, which is indicated by the arrows within the depiction of circulator. Essentially, RF signals may be conveyed between the circulator ports-in the indicated direction (clockwise), and not in the opposite direction (counter-clockwise). Accordingly, during normal operations, signals may be conveyed through the circulatorfrom the first portto the second port, and from the second portto the third port, but not directly from the first portto the third portor directly from the third portto the second port.

110 210 108 208 110 210 1 2 FIGS., 1 2 FIGS., 1 2 FIGS., As indicated above, the driver amplification stage,() of an RF transmitter,() may include various embodiments of Doherty power amplifiers. Further, one or more embodiments of a driver amplification stage,() may include features that enable the driver amplification stage to be easily “tuned” for high-efficiency operation within a particular operational frequency band, simply by changing one or more discrete components (e.g., discrete capacitors) that are coupled to the driver amplification stage.

3 7 FIGS.- 3 7 FIGS.- 3 7 FIGS.- 3 7 FIGS.- 3 7 FIGS.- 1 FIG. 322 422 622 722 380 380 480 480 580 580 680 680 780 780 327 327 427 427 527 1 527 2 527 1 527 2 383 383 483 483 108 108 As will be described in detail below in conjunction with, substantial portions of the Doherty power amplifiers for a driver amplification stage may be implemented in a packaged amplifier device (e.g., devices,,,,), and embodiments of output combiner circuits (e.g., circuits,′,,′,,′,,′,,′,) of those Doherty power amplifiers include access points (e.g., shunt circuit access terminals,′,,′,-,-,-′,-′,) that enable tuning components (e.g., capacitors,′,,′,) to be electrically coupled to the output combiner circuits. The values of the tuning components (e.g., the capacitance values) may be selected to “tune” each Doherty power amplifier for high-performance operation at various operational frequencies. In other words, when a tuning component includes a first capacitor with a first capacitance value, inclusion of that first capacitor in an output combiner circuit may tune the Doherty power amplifier for high-performance operation within a first operational frequency band (e.g., 1805-1880 megahertz (MHz)). Conversely, when a tuning component includes a second capacitor with a second capacitance value, inclusion of that second capacitor in an output combiner circuit may tune the Doherty power amplifier for high-performance operation within a second and different operational frequency band (e.g., 2110-2170 MHz). Again, this has the advantageous effect of allowing each of multiple transmitters (e.g., transmitters,) to have a similar or exactly the same layout, even though the multiple transmittersmay be tuned to operate at different operational frequencies.

110 210 1 2 FIGS., 3 7 FIGS.- Various embodiments of amplification stages that may be particularly well suited for use as a driver amplification stage (e.g., amplification stages,,) in an RF transmitter of a cellular base station transmitter will now be described in conjunction with. It should be noted here that the embodiments of amplification stages illustrated and described herein may be used in contexts other than as a driver amplification stage in a cellular base station transmitter (e.g., the various embodiments may be used in systems other than cellular base station transmitters, and/or the various embodiments may be used in other stages of a transmitter lineup). Accordingly, implementation of the various embodiments is not limited to use in a cellular base station transmitter, and more particularly, is not limited to use as a driver amplification stage.

350 350 350 350 3 FIG. 6 FIG. 3 FIG. 6 FIG. It is noted here that, for the convenience and understandability of the reader, components or circuits in the various drawings that correspond to exactly the same thing have identical reference numbers (e.g., power amplifierinis the same as power amplifierin). For brevity, the entirety of the description of characteristics of a particular component or circuit may not be repeated verbatim in the descriptions of all figures in which the component is included. However, it is to be understood that, when the characteristics of a component or circuit with a particular reference number is described in detail in conjunction with the description of a particular figure (e.g., power amplifierin), the described details are incorporated by reference into the description of the same-numbered component or circuit in conjunction with a different figure (e.g., power amplifierin).

322 422 422 622 722 322 622 3 7 FIGS.- 3 FIG. 6 FIG. Further, components or circuits in the various drawings that correspond to different embodiments of a component or circuit (“analogous components”) may be identified with similar reference numbers that have the same last two digits. For example, analogous components identified by similar reference numbers,,′,,ineach correspond to different embodiments of a packaged amplifier device. Again, for brevity, to the extent that characteristics of analogous components or circuits are the same in different figures, those characteristics may not be repeated verbatim in the descriptions of all figures in which the analogous components are included. Instead, the descriptions may focus on the differences between characteristics of the analogous components. However, it is to be understood that, when characteristics of analogous components or circuits with reference numbers having the same last two digits are described in detail in conjunction with the description of a particular figure (e.g., packaged amplifier devicein), as long as differences are not specifically identified, the described details are incorporated by reference into the description of the similarly-numbered component or circuit in conjunction with a subsequent figure (e.g., packaged amplifier devicein).

3 FIG. 1 2 FIGS., 3 FIG. 4 FIG. 3 FIG. 310 110 210 410 is a schematic drawing of an amplification stage(e.g., amplification stage,,) that includes a dual 90/0 Doherty power amplifier with tunable output combiner circuits, in accordance with an example embodiment. For enhanced understanding,should be viewed simultaneously with, which is a top view of a physical implementation of an amplification stagethat includes the dual 90/0 Doherty power amplifier of.

316 316 416 416 380 380 480 480 350 450 386 386 486 486 90 370 470 386 386 486 486 3 FIG. 4 FIG. 3 4 FIGS., 3 4 FIGS., 3 4 FIGS., 3 4 FIGS., 3 4 FIGS., Some terminology may be useful at this point. In particular, the term “dual Doherty power amplifier” means an amplifier that includes two Doherty power amplifiers (e.g., amplifiers,′,, or,′,) that are implemented in parallel with each other in an amplification circuit. Further, the term “90/0 Doherty power amplifier” means a Doherty power amplifier that has an output combining circuit (e.g., circuits,′,,′,) in which an electrical length between the output of one amplifier or amplifier die (e.g., amplifieror amplifier die,) and a combining node (e.g., combining node,′,,′,) is aboutdegrees (i.e., exactly 90 degrees or between about 85 and 95 degrees), and in which an electrical length between the output of another amplifier or amplifier die (e.g., amplifieror amplifier die,) and a combining node (e.g., combining node,′,,′,) is about zero degrees (although there may be a minimal electrical length).

3 4 FIGS.and 1 2 FIGS., 1 2 FIGS., 310 410 301 401 101 201 310 410 110 210 310 410 Referring now to, an amplification stage,includes various circuitry and devices housed on a transmitter substrate,(e.g., transmitter substrate,,). As mentioned above, the amplification stage,may correspond to a driver amplification stage (e.g., amplification stages,,) in an RF transmitter of a cellular base station transmitter, although the amplification stage,is not limited to that particular application or location along a transmitter lineup.

310 410 301 401 316 416 316 416 310 410 311 411 312 412 316 416 316 416 388 488 392 492 The amplification stage,essentially includes a dual 90/0 Doherty power amplifier coupled to the transmitter substrate,, which includes a first Doherty power amplifier,and a second Doherty power amplifier′,′ arranged in parallel (e.g., in quadrature). More particularly, amplification stage,includes a transmitter input terminal,, a first signal power splitter,, the first Doherty power amplifier,, the second Doherty power amplifier′,′, a signal power combiner,, and a transmitter output terminal,.

312 412 301 401 312 412 312 412 312 412 313 314 315 312 412 485 301 401 485 301 401 301 401 3 FIG. 4 FIG. 4 FIG. The first signal power splitter,is physically coupled to the transmitter substrate,. The first signal power splitter,may have any of a variety of configurations. For example, the first signal power splitter,may be a splitter selected from a Wilkinson-type splitter, a hybrid quadrature splitter, or another suitable type of splitter. Either way, the first signal power splitter,has a first splitter input terminal, a first splitter output terminal, and a second splitter output terminal. Although not indicated in(but as shown in), the first signal power splitter,also may include an additional terminal that is coupled through a resistive termination to a ground reference (e.g., ground reference,) of the transmitter substrate,. For example, the ground referenceif the transmitter substrate,may be a conductive ground plane embedded within the transmitter substrate,.

313 301 401 311 411 209 314 301 401 316 416 316 416 318 317 417 315 301 401 316 416 316 416 318 317 417 2 FIG. The first splitter input terminalis electrically coupled through a conductive trace on substrate,to the transmitter input terminal,, and is configured to receive an input RF signal for amplification (e.g., an input RF signal from TX signal processor,). The first splitter output terminalis electrically coupled through another conductive trace on substrate,to an input to the first Doherty power amplifier,. In the illustrated embodiment, the input to the first Doherty power amplifier,corresponds to an input terminalof a second signal power splitter,. Similarly, the second splitter output terminalis electrically coupled through yet another conductive trace on substrate,to an input to the second Doherty power amplifier′,′. In the illustrated embodiment, the input to the second Doherty power amplifier′,′ corresponds to an input terminal′ of a second signal power splitter′,′.

313 313 311 312 412 314 316 416 315 316 416 The first splitter input terminalis configured to receive, at input terminal, an input RF signal from RF input, and to divide the power of the input RF signal into first and second RF input signals. The first signal power splitter,divides the power of the input RF signal such that about half of the input RF signal power is provided to the first splitter output terminal(and thus to the first Doherty power amplifier,), and about half of the input RF signal power is provided to the second splitter output terminal(and thus to the second Doherty power amplifier′,′).

310 410 316 316 416 416 312 412 388 488 388 488 301 401 312 388 488 388 488 388 488 389 390 391 388 488 485 301 401 3 FIG. 4 FIG. 4 FIG. Details of the dual 90/0 Doherty power amplifier (e.g., amplification stage,) will be described in detail later. Briefly, each of the first and second Doherty power amplifiers,′,,′ of the dual 90/0 Doherty power amplifier is electrically coupled between the first signal power splitter,and a signal power combiner,. The signal power combiner,is physically coupled to the transmitter substrate,. As with the first signal power splitter, the signal power combiner,may have any of a variety of configurations. For example, the signal power combiner,may be a combiner selected from a Wilkinson-type combiner, a hybrid quadrature combiner, or another suitable type of combiner. Either way, the signal power combiner,has a first combiner input terminal, a second combiner input terminal, and a combiner output terminal. Although not indicated in(but as shown in), the signal power combiner,also may include an additional terminal that is coupled through a resistive termination to a ground reference (e.g., ground reference,) of the transmitter substrate,.

389 301 401 316 416 326 316 416 389 390 301 401 316 416 326 316 416 390 388 488 391 391 301 401 392 492 392 492 The first combiner input terminalis electrically coupled through yet another conductive trace on substrate,to an output of the first Doherty power amplifier,(e.g., to terminal). A first amplified RF output signal from the first Doherty power amplifier,is received at the first combiner input terminal. Similarly, the second combiner input terminalis electrically coupled through yet another conductive trace on substrate,to an output of the second Doherty power amplifier′,′ (e.g., to terminal′). A second amplified RF output signal from the second Doherty power amplifier′,′ is received at the second combiner input terminal. The signal power combiner,is configured to combine the power of the first and second amplified RF output signals into a third amplified RF output signal, which is provided at the combiner output terminal. The combiner output terminalis electrically coupled through yet another conductive trace on substrate,to the transmitter output terminal,, and accordingly, the third amplified RF output signal is provided to the transmitter output terminal,.

310 410 316 316 416 416 311 411 310 410 311 411 312 412 388 488 392 492 310 410 As the above description indicates, of the dual 90/0 Doherty power amplifier (i.e., amplification stage,) basically has two parallel amplification paths (i.e., the first and second Doherty power amplifiers,′,,′). The power of an input RF signal provided at an input,to the amplification stage,(at input,) is equally divided (by the first power splitter,) into first and second RF input signals, which are separately amplified through the parallel amplification paths. The resulting first and second amplified RF output signals are then combined (by the signal power combiner,), and provided as the third amplified RF output signal at the transmitter output terminal,of the amplification stage,.

316 316 416 416 316 316 416 416 316 316 416 416 301 401 322 422 322 422 301 401 322 422 301 401 322 422 The first and second Doherty power amplifiers,′,,′ will now be described in more detail. According to one or more embodiments, the first and second Doherty power amplifiers,′,,′ may be implemented using substantially the same circuit configuration (e.g., the same components electrically coupled together in the same manner). Generally, each of the first and second Doherty power amplifiers,′,,′ has some circuitry (“external circuitry”) that is directly physically connected to the first transmitter substrate,, and other circuitry (“internal circuitry”) that is housed within an RF amplifier device,. The RF amplifier device,is directly physically connected to the mounting surface of the first transmitter substrate,. In other words, the RF amplifier device,is a discrete, surface-mount component. As will be described in detail below, the “external circuitry” that is directly connected to the first transmitter substrate,electrically communicates with the “internal circuitry” that is housed within the RF amplifier device,through various device terminals.

316 316 416 416 322 422 322 422 323 423 323 423 421 324 324 325 325 326 326 327 327 424 424 425 425 426 426 427 427 323 423 Before describing additional details of the circuitry of the first and second Doherty power amplifiers,′,,′, the structure of the RF amplifier device,will first be described. According to one or more embodiments, the RF amplifier device,includes a discrete package body,. According to one or more embodiments, the discrete package body,includes a conductive flangeand a plurality of conductive device terminals,′,,′,,′,,′,,′,,′,,′,,′, which are held in a fixed physical relationship by rigid non-conductive material of the discrete package body,(e.g., by ceramic or plastic encapsulation).

4 FIG. 4 FIG. 323 423 324 327 324 327 424 427 424 427 322 422 322 422 323 423 323 423 323 423 323 423 324 327 324 327 424 427 424 427 323 423 324 327 324 327 424 427 424 427 323 423 324 327 324 327 424 427 424 427 323 423 422 It should be mentioned here that, althoughdepicts a certain type of package body,and a certain type of device terminals-,′-′,-,′-′, the RF amplifier device,may have any of a variety of form factors. For example, the RF amplifier device,may include a surface-mount type of package body,, in some embodiments, or may include a through-hole type of package body,, in other embodiments. Surface-mount types of package bodies,may include, for example, flat packages (e.g., dual flat packages or quad flat packages), chip-scale packages, ball grid arrays, pin grid arrays, leaded or leadless chip carriers, or other types of packages. In some other embodiments, the package body,may include a small multi-layer PCB, where the device terminals may include through substrate vias that contact conductive pads on the bottom of the PCB. Each of the device terminals-,′-′,-,′-′ has a form factor that is appropriate for the type of package body,. For example, each of the device terminals-,′-′,-,′-′ may be “leadless” terminals that do not extend beyond the package body,. Alternatively, each of the device terminals-,′-′,-,′-′ may be “leaded” terminals (e.g., gull-wing terminals) that extend beyond the package body,. For purposes of illustration and not by way of limitation,shows an RF amplifier devicewith a dual flat package (DFP) configuration.

323 423 421 324 327 324 327 424 427 424 427 421 324 327 324 327 424 427 424 427 323 423 423 324 327 324 327 424 427 424 427 422 401 422 422 4 FIG. 4 FIG. More specifically, the discrete package body,includes a central conductive flangeand a plurality of device terminals-,′-′,-,′-′, all of with are embedded in non-conductive material (e.g., ceramic or plastic encapsulant). A component mounting surface of the conductive flangeand “proximal ends” of the device terminals-,′-′,-,′-′ are exposed within an interior of the package body,. As will be described in more detail below, various electrical components are physically and electrically coupled to a mounting surface of the conductive flange, and are electrically coupled to the proximal ends of the device terminals-,′-′,-,′-′ through wirebonds or other conductors. A non-conductive cover may enclose the electrical components and wirebonds in an air cavity, in some embodiments. In other embodiments, the electrical components and wirebonds may be covered with a non-conductive encapsulant material (e.g., plastic encapsulant). In, the upper image showing RF amplifier devicemounted to the transmitter substrateshows a top surface of the RF amplifier device, which is defined by an outer surface of the non-conductive cover or the non-conductive encapsulant material, which obscures the internal circuitry. For improved visibility, the lower image inshows an enlarged image of the RF amplifier device, with the cover or non-conductive encapsulant material removed so that the internal circuitry can be seen.

421 324 327 324 327 424 427 424 427 323 423 323 423 421 322 422 421 301 401 422 324 327 324 327 424 427 424 427 301 401 316 316 416 416 322 422 316 316 416 416 324 327 324 327 424 427 424 427 An outer surface of the conductive flangeand “distal ends” of the device terminals-,′-′,-,′-′ are exposed at an exterior of the package body,(e.g., at a bottom surface of the package body,). The conductive flangemay function as a ground reference and/or heat dissipation structure for at least some of the electrical components within the device,, and the exposed outer surface of the conductive flangeenables the interior circuitry to be electrically and thermally coupled to additional conductive structures of the transmitter substrate,(not shown, but located directly underneath device). Additionally, the distal ends of the device terminals-,′-′,-,′-′ are physically and electrically coupled (e.g., through solder or other conductive connections) to conductive pads or traces (not numbered) at the top surface of the transmitter substrate,. In this manner, the external circuitry of each Doherty power amplifier,′,,′ may be electrically connected to the internal circuitry (within device,) of each Doherty power amplifier,′,,′ through the device terminals-,′-′,-,′-′.

316 316 416 416 350 350 450 450 370 370 470 470 421 323 423 350 350 450 450 370 370 470 470 450 450 470 470 351 351 371 371 451 451 471 471 352 352 372 372 452 452 472 472 3 FIG. 4 FIG. 3 FIG. 4 FIG. As will be discussed in more detail below, each Doherty power amplifier,′,,′ includes a carrier amplifier,′,,′ and a peaking amplifier,′,,′. According to one or more embodiments, each carrier and peaking amplifier is implemented with a power transistor integrated within a power transistor semiconductor die coupled to the mounting surface of the conductive flangeof the package body,. For example, carrier amplifiers,′ () may be physically implemented with carrier amplifier dies,′ (), and peaking amplifiers,′ () may be physically implemented with peaking amplifier dies,′ (). For example, each of the power transistor(s) within each of the amplifier dies,′,,′ may be a field effect transistor (FET), such as a laterally-diffused metal oxide semiconductor (LDMOS) FET or a high electron mobility transistor (HEMT). The description may refer to each transistor as including an amplifier input terminal,′,,′,,′,,′, a first amplifier output terminal,′,,′,,′,,′, and a second amplifier output terminal (not numbered). For example, using terminology associated with FETs, an “amplifier input terminal” refers to a gate terminal of a transistor, a “first amplifier output terminal” refers to a drain terminal of the transistor, and a “second amplifier output terminal” refers a source terminal of the transistor. Although the below description may use terminology commonly used in conjunction with FET devices, the various embodiments are not limited to implementations the utilize FET devices, and instead are meant to apply also to implementations that utilize bipolar junction transistors (BJT) devices or other suitable types of transistors.

450 450 470 470 450 450 470 470 In some embodiments, each carrier amplifier die,′ and peaking amplifier die,′ more specifically includes a gallium nitride (GaN) HEMT. In other embodiments, each of the carrier amplifier die,′ and peaking amplifier die,′ may include silicon-based power transistors, or power transistors formed using other semiconductor technologies (e.g., silicon germanium (SiGe) and/or gallium arsenide (GaAs)).

316 416 318 317 417 326 426 322 422 317 417 330 360 380 324 330 325 360 The first Doherty power amplifier,of the dual 90/0 Doherty power amplifier includes an RF input (e.g., corresponding to an input terminalof splitter,), an RF output (e.g., corresponding to a first output terminal,of device,), a signal splitter,(referred to herein as a “second signal splitter”), a carrier amplification path, a peaking amplification path, and an output combiner circuit. The first amplifier input terminalcorresponds to an input terminal for the carrier amplification path, and the second amplifier input terminalcorresponds to an input terminal for the peaking amplification path.

316 416 318 317 417 326 426 322 422 317 417 330 360 380 324 330 325 360 Similarly, the second Doherty power amplifier′,′ of the dual 90/0 Doherty power amplifier includes an RF input (e.g., corresponding to an input terminal′ of splitter′,′), an RF output (e.g., corresponding to a second output terminal′,′ of device,), a signal splitter′′ (referred to herein as a “third signal splitter”), a carrier amplification path′, a peaking amplification path′, and an output combiner circuit′. The third amplifier input terminal′ corresponds to an input terminal for the carrier amplification path′, and the fourth amplifier input terminal′ corresponds to an input terminal for the peaking amplification path′.

316 316 416 416 314 315 312 412 318 318 316 316 416 416 317 317 417 417 314 315 312 412 330 330 360 360 350 350 370 370 380 380 326 326 426 426 322 422 301 401 389 390 388 488 388 488 391 391 392 492 301 401 Briefly, during operation of the dual 90/0 Doherty power amplifier, within each of the first and second Doherty power amplifiers,′,,′, the power of an input RF signal (e.g., the first or second RF signals produced at output terminals,, respectively, of the first signal power splitter,) is provided at an RF input (e.g., splitter input terminalor′) to the first or second Doherty power amplifier,′,,′. Each of the second and third signal splitters,′,,′ divides the power of the first or second RF signal (produced at output terminals,of splitter,) into a carrier RF signal and a peaking RF signal. Each carrier RF signal is amplified along the carrier amplification path,′, and each peaking RF signal is amplified along the peaking amplification path,′. The amplified carrier and peaking RF signals produced by the carrier and peaking amplifiers,′,,′ are then combined through an output combining circuit,′. A resulting first or second amplified RF output signal is then conveyed through an output terminal,′,,′ of the device,and through a conductive trace on the transmitter substrate,to a first or second combiner input,of the signal power combiner,. The signal power combiner,then combines the power of the first and second amplified RF output signals, and produces a combined amplified RF output signal at combiner output. The combined amplified RF output signal is then conveyed from combiner outputto the transmitter output terminal,through another conductive trace on the transmitter substrate,.

200 100 392 492 190 290 190 290 194 294 299 1 2 FIGS., 1 2 FIGS., 1 2 FIGS., 1 2 FIGS.and 1 2 FIGS., 2 FIG. When incorporated into a larger system (e.g., a transmitterof a cellular radio system()), the transmitter output terminal,is electrically coupled to the input to a final stage amplifier (e.g., amplifier,,). The output of the final stage amplifier (e.g., amplifier,,), in turn, is coupled to a load. For example, as discussed in conjunction with, the load may include a circulator (e.g., circulator,,) and an antenna (e.g., antenna,), or another type of load.

316 316 416 416 330 330 360 360 316 316 416 416 360 360 Each Doherty power amplifier,′,,′ is considered to be a “two-way” Doherty power amplifier, which includes one carrier amplification path,′ and one peaking amplification path,′. In other embodiments, each Doherty power amplifier,′,,′ may include one or more additional peaking amplification paths (not shown) in parallel with peaking amplification path,′.

316 316 416 416 316 316 416 416 350 350 370 370 450 450 470 470 316 316 416 416 350 350 370 370 450 450 470 470 370 370 350 350 Further, in various embodiments, each Doherty power amplifier,′,,′ may be a “symmetric” or an “asymmetric” amplifier. When a Doherty power amplifier,′,,′ is a “symmetric” amplifier, the relative sizes of the carrier and peaking amplifiers,′,,′ (i.e., the size of dies,′,,′) are approximately equal to each other. Conversely, when a Doherty power amplifier,′,,′ is an “asymmetric” amplifier, the relative sizes of the carrier and peaking amplifiers,′,,′ (i.e., the size of dies,′,,′) are different from each other. Typically, in an asymmetric Doherty power amplifier, the peaking amplifier,′ is larger than the carrier amplifier,′.

350 350 370 370 450 450 470 470 450 450 470 470 470 470 450 450 More specifically, as used herein, the term “size,” when referring to a physical characteristic of a power amplifier or power transistor, refers to the periphery or the current carrying capacity of the transistor(s) associated with that amplifier or transistor. The term “symmetric,” when referring to the relative sizes of carrier and peaking amplifiers,′ and,′, means that the size of the power transistor(s) within the carrier amplifier dies,′ is/are substantially identical to (i.e., within 5%) the size of the power transistor(s) within the peaking amplifier dies,′. Conversely, the term “asymmetric” means that the size of the power transistor(s) within the carrier amplifier dies,′ is/are significantly different from the size of the power transistor(s) within the peaking amplifier dies,′ (e.g., the size of the power transistor(s) within the peaking amplifier dies,′ is/are from 50% to 100% or more than the size of the power transistor(s) within the carrier amplifier dies,′). Accordingly, for example, when the ratio of carrier amplifier size to peaking amplifier size (or the “carrier-to-peaking ratio”) is denoted as x: y (where x corresponds to relative carrier amplifier size and y corresponds to relative peaking amplifier size), a ratio of 1:1 would be symmetric, and a ratio of 1:2 would be asymmetric, according to the above definitions.

316 316 416 416 316 316 416 416 318 317 417 318 318 421 312 412 314 315 The configuration of each Doherty power amplifier,′,,′ will now be discussed in more detail. In each Doherty power amplifier,′,,′, the RF input (e.g., the input terminalof the signal splitter,or the input terminal′ of the signal splitter′,′) is configured to receive either the first or the second input RF signal from the first signal splitter,(i.e., from the first signal splitter output terminalor from the second signal splitter output terminal).

317 317 417 417 301 401 317 317 417 417 317 317 417 417 317 317 417 417 318 318 314 315 312 319 319 320 320 317 317 417 417 485 301 401 3 FIG. 4 FIG. 4 FIG. The second and third signal power splitters,′,,′ are physically coupled to the transmitter substrate,. The second and third signal splitters,′,,′ may have any of a variety of configurations. For example, each of signal splitters,′,,′ may be a splitter selected from a Wilkinson-type splitter, a hybrid quadrature splitter, or another suitable type of splitter. Either way, each signal splitter,′,,′ has an input,′ coupled to an output terminal,of the first signal splitter, and two outputs,′,,′. Although not indicated in(but as shown in), each of the second and third signal splitters,′,,′ also may include an additional terminal that is coupled through a resistive termination to a ground reference (e.g., ground reference,) of the transmitter substrate,.

319 319 330 330 301 401 324 324 320 320 370 370 301 401 325 325 317 317 417 417 318 318 312 412 317 317 417 417 319 319 330 330 320 320 360 360 A first signal splitter output,′ is coupled to the carrier amplification path,′ through a conductive trace on the transmitter substrate,and through the first or third amplifier input terminal,′. A second signal splitter output,′ is coupled to the peaking amplification path,′ through another conductive trace on the transmitter substrate,and through the second or fourth amplifier input terminal,′. Essentially, each signal splitter,′,,′ is configured to receive, at its input,′, one of the first or second RF input signals from the first signal splitter,, and to divide the power of the received input RF signal into a carrier RF signal and a peaking RF signal. Each signal splitter,′,,′ is further configured to provide, at the first signal splitter output,′, the carrier RF signal for the carrier amplification path,′, and to provide, at the second signal splitter output,′, the peaking RF signal for the peaking amplification path,′.

351 351 371 371 350 350 370 370 380 380 480 480 317 317 417 417 320 320 319 319 317 317 417 417 319 319 320 320 320 320 370 370 Proper operation of a Doherty power amplifier requires the carrier RF signal to be about 90 degrees out of phase with the peaking RF signal when those signals arrive at the inputs,′,,′ to the carrier and peaking amplifiers,′,,′, respectively. This 90 degree phase difference is implemented at the input to the Doherty power amplifier in order to compensate for a 90 degree phase shift applied at the output of the Doherty power amplifier (e.g., a 90 degree phase shift applied by output combiner circuit,′,,′), as will be discussed later. In some embodiments (e.g., when hybrid quadrature splitters are used), the first and second signal splitters,′,,′ are configured to produce a peaking RF signal at the second signal splitter output,′ that is about 90 degrees out of phase from (e.g., delayed from) the carrier RF signal produced at the first signal splitter output,′. In other embodiments (e.g., when Wilkinson-type splitters are used), the first and second signal splitters,′,,′ are configured to produce carrier and peaking RF signals at the first and second signal splitter outputs,′,,′ that are in phase with each other, and the above-mentioned 90 degree phase difference between the carrier and peaking RF signals may be imparted through a first series of conductive elements (described below) between the second signal splitter output,′ and the peaking amplifier,′.

310 330 330 326 326 426 426 325 325 370 370 350 350 370 370 330 330 310 330 330 360 360 325 325 370 370 330 330 360 360 During operation of the amplification stagein a relatively low-power mode (i.e., when the power of the input RF signal is below a threshold), only the carrier amplification paths,′ supply current to the load (through amplifier output terminals,′,,′). In such circumstances, the RF signal level at the peaking amplifier input terminal,′, is below the threshold to turn on the peaking amplifier,′. Thus, the combined power from the carrier and peaking amplifiers,′,,′ is substantially from the carrier amplification path,′. Conversely, during operation of the amplification stagein a relatively high-power mode (i.e., when the power of the input RF signal is above a threshold), both the carrier and peaking amplification paths,′,,′ supply current to the load. In such circumstances, the RF signal level at the peaking amplifier input terminal,′ is above the threshold to turn on the peaking amplifier,′. Thus, both the carrier and peaking amplifier paths,′,,′ contribute to the combined power.

317 317 316 316 350 350 370 370 316 316 317 317 330 330 360 360 316 316 316 316 317 317 316 316 317 317 330 330 360 360 Each of the second and third signal splitter,′ divides the power of the input RF signal according to a carrier-to-peaking size ratio. For example, when Doherty power amplifier,′ has a symmetric configuration in which the carrier amplifier,′ and the peaking amplifier,′ are substantially equal in size (i.e., the Doherty power amplifier,′ has a 1:1 carrier-to-peaking size ratio), each of the second and third signal splitter,′ may divide the power of the input RF signal such that about half of the input RF signal power is provided to the carrier amplification path,′, and about half of the input RF signal power is provided to the peaking amplification path,′. Conversely, when Doherty power amplifier,′ has an asymmetric configuration (e.g., the Doherty power amplifier,′ has a 1:x carrier-to-peaking size ratio, where x>1), each of the second and third signal splitter,′ may divide the power unequally. For example, when Doherty power amplifier,′ has a 1:2 carrier-to-peaking size ratio, each of the second and third signal splitter,′ may divide the power of the input RF signal such that a third of the input signal power is provided to the carrier amplification path,′, and two thirds of the input signal power is provided to the peaking amplification path,′.

351 351 371 371 350 350 370 370 317 317 330 330 319 319 351 351 360 360 320 320 371 371 317 317 360 360 320 320 371 371 330 330 319 319 351 351 360 360 301 401 320 320 325 325 319 319 324 324 360 360 322 422 In addition, as mentioned above, the peaking input RF signal should be about 90 degrees out of phase with (delayed from) the carrier input RF signal when those signals arrive at the inputs,′,,′ to the carrier and peaking amplifiers,′,,′, respectively. In embodiments in which the signal splitter,′ is configured to produce carrier and peaking input RF signals that are 90 degrees out of phase with each other (e.g., when hybrid quadrature splitters are used), the phase shift applied along the carrier amplification path,′ between the first signal splitter output,′ and the carrier amplifier input,′ may be about equal to the phase shift applied along the peaking amplification path,′ between the second splitter output,′ and the peaking amplifier input,′. Conversely, when the signal splitter,′ is not configured to produce carrier and peaking input RF signals that are 90 degrees out of phase with each other (e.g., when Wilkinson-type splitters are used), the phase shift applied along the peaking amplification path,′ between the second signal splitter output,′ and the peaking amplifier input,′ may be 90 degrees greater than the phase shift applied along the carrier amplification path,′ between the first splitter output,′ and the carrier amplifier input,′. The additional 90 degrees of phase shift along the peaking amplification path,′ may be achieved on the transmitter substrate,through a longer conductive trace (e.g., a conductive trace that is 90 degrees longer) between the second signal splitter output,′ and the second or fourth amplifier input terminal,′ than the conductive trace between the first signal splitter output,′ and the first or third amplifier input terminal,′. Alternatively, the additional 90 degree delay along the peaking amplification path,′ may be achieved using internal circuitry within the device,.

330 330 319 319 386 386 486 486 380 380 480 480 330 330 319 319 350 350 450 450 350 350 450 450 381 381 382 382 481 481 482 482 380 380 480 480 330 330 301 401 319 319 324 324 424 424 324 324 424 424 322 422 334 334 434 434 322 422 324 324 424 424 350 350 The carrier amplification path,′ is coupled between the first splitter output,′ and a combining node,′,,′ of the output combiner circuit,′,,′. Each carrier amplification path,′ includes, a series of conductive elements between the first splitter output,′ and the carrier amplifier,′,,′, the carrier amplifier,′,,′, and inductive elements,′,,′,,′,,′ of a phase shift and impedance inversion circuit within the output combiner circuit,′,,′. The series of conductive elements of the carrier amplification path,′ includes: 1) a conductive trace (not numbered) on the transmitter substrate,between the first splitter output,′ and the first or third amplifier input terminals,′,,′; 2) one of the first or third amplifier input terminals,′,,′ of the device,; and 3) an inductive element,′ (e.g., one or more wirebonds,′) within the device,between the first or third amplifier input terminal,′,,′ and the carrier amplifier,′.

324 324 424 424 301 401 334 334 434 434 324 324 424 424 351 351 451 451 350 350 450 450 334 334 434 434 324 324 424 424 351 351 451 451 350 350 450 450 334 334 434 434 332 332 332 332 332 332 334 334 434 434 4 FIG. Distal ends of the first and third amplifier input terminals,′,,′ are coupled (e.g., soldered) to ends of the conductive traces (or to conductive pads) on the transmitter substrate,. Each inductive element,′,,′ provides an electrical connection between one of the first and third amplifier input terminals,′,,′ and an input,′,,′ to the carrier amplifier,′,,′. As shown in, each inductive element,′ may be implemented as one or more wirebonds,′ between the first or third amplifier input terminals,′,,′ and the input,′,,′ to the carrier amplifier,′,,′. In addition, the inductive element,′,,′ may form a portion of an optional carrier IMN,′. When included, the carrier IMN,′ is configured to incrementally increase the circuit impedance. For example, but not by way of limitation, the carrier IMN,′ may include, for example, a lowpass or bandpass circuit configured as a T- or pi-impedance matching network, where the inductive element,′,,′ provides a series inductance in the circuit.

350 350 450 450 421 323 423 350 350 450 450 351 351 451 451 351 351 451 451 334 334 434 434 332 332 324 324 350 350 450 450 352 352 452 452 350 350 450 450 350 350 450 450 421 As mentioned above, each carrier amplifier,′ may be implemented as a power transistor in a carrier amplifier die,′, which is physically and electrically coupled to the conductive flangeof the package body,. As used herein, “carrier amplifier” and “carrier amplifier die” may be used interchangeably. Each carrier amplifier,′,,′ has a carrier amplifier input,′,,′ (e.g., a gate terminal) and two current-carrying terminals (e.g., drain and source terminals). As indicated above, the carrier amplifier input,′,,′ is coupled through inductive element,′,,′ (and/or through the carrier IMN,′) to the first or third amplifier input terminal,′. One of the current-carrying terminals (e.g., the drain terminal) of the carrier amplifier,′,,′ functions as a carrier amplifier output,′,,′, at which an amplified carrier signal is produced by the carrier amplifier,′,,′. The other current-carrying terminal (e.g., the source terminal) of the carrier amplifier,′,,′ may be coupled to a ground reference node (e.g., to the conductive flange).

350 350 450 450 351 351 451 451 352 352 452 452 352 352 452 452 350 350 450 450 380 380 480 480 380 380 480 480 352 352 452 452 380 380 480 480 381 381 382 382 481 481 482 482 383 383 483 483 386 386 486 486 386 386 486 486 372 372 472 472 370 370 470 470 327 327 427 427 485 301 401 The carrier amplifier,′,,′ is configured to amplify the carrier input RF signal received at the carrier amplifier input,′,,′, and to produce an amplified carrier signal at the carrier amplifier output,′,,′. The output,′,,′ (e.g., drain terminal) of the carrier amplifier,′,,′ is electrically coupled to the output combiner circuit,′,,′. The output combiner circuit,′,,′ is configured to provide an impedance inversion, and also to impart a phase shift to the amplified carrier signal produced at the carrier amplifier output,′,,′. According to one or more embodiments, each output combiner circuit,′,,′ includes first and second, series-connected inductive elements,′,,′ (e.g., one or more first wirebonds,′ and one or more second wirebonds,′), a shunt capacitor,′,,′, and a combining node,′,,′. As will be discussed in more detail later, the combining node,′,,′ may be co-located with the output,′,,′ of the peaking amplifier,′,,′. Further, as used herein, the term “shunt” means electrically coupled between a circuit node (e.g., terminal,′,,′) and a ground reference node (or other DC voltage reference). The ground reference node may be, for example, a ground referenceof the transmitter substrate,.

381 381 382 382 481 481 482 482 352 352 452 452 386 386 486 486 327 327 427 427 381 381 382 382 481 481 482 482 381 381 481 481 352 352 452 452 327 327 427 427 382 382 482 482 327 327 427 427 386 386 486 486 352 352 452 452 381 381 382 382 According to one or more embodiments, the first and second inductive elements,′,,′,,′,,′ are coupled in series between the carrier amplifier output,′,,′ and the combining node,′,,′, with an intermediate node (corresponding to shunt circuit access terminals,′,,′) between each series-connected set of first and second inductive elements,′,,′,,′,,′. For example, each first inductive element,′ may be implemented as a first set of wirebonds,′, where each wirebond has a first end coupled to the carrier amplifier output,′,,′, and a second end coupled to the shunt circuit access terminal,′,,′. Each second inductive element,′ may be implemented as a second set of wirebonds,′, where each wirebond has a first end coupled to the shunt circuit access terminal,′,,′, and a second end coupled to the combining node,′,,′ (e.g., to the peaking amplifier output,′,,′). In alternate embodiments, the first and second inductive elements,′,,′ may be implemented using conductive traces, rather than wirebonds.

381 381 382 382 481 481 482 482 381 381 382 382 481 481 482 482 352 352 452 452 386 386 486 486 386 386 486 486 According to one or more embodiments, the total electrical length of the first and second inductive elements,′,,′,,′,,′ is about 90 degrees (i.e., exactly 90 degrees or between about 85 and 95 degrees). Accordingly, the first and second inductive elements,′,,′,,′,,′ impart about 90 degrees of phase delay to the amplified carrier signal between the carrier amplifier output,′,,′ and the combining node,′,,′. As discussed in more detail below, this phase shift has the result of phase-aligning the amplified carrier signal with the amplified peaking signal when they arrive at the combining node,′,,′.

4 FIG. 427 427 484 484 301 401 383 383 483 483 301 401 484 484 485 301 401 383 383 483 483 484 484 485 301 401 As best shown in, each shunt circuit access terminal,′ (or “intermediate node”) is coupled to a conductive pad,′ on the transmitter substrate,. Further, according to one or more further embodiments, a shunt capacitor,′,,′ is coupled to the transmitter substrate,between the conductive pad,′ and a ground referenceof the transmitter substrate,. More specifically, each shunt capacitor,′,,′ may have a first terminal connected to the conductive pad,′, and a second terminal coupled to a ground referenceof the transmitter substrate,.

3 4 FIGS.and 5 FIG. 483 483 322 422 327 327 427 427 422 527 1 527 1 527 2 527 2 422 483 483 422 In the embodiment illustrated in, the shunt capacitors,′ form portions of the external circuitry, and they are electrically coupled with the internal circuitry of device,through a single shunt circuit access terminal,′,,′. Referring briefly to, according to an alternate embodiment, an RF amplifier device′ may include two shunt circuit access terminals-,-′,-,-′ to provide access from the internal circuitry of device′ to shunt capacitors,′ that are external to the device′.

422 422 422 422 422 422 422 422 422 5 FIG. 4 FIG. RF amplifier device′ () is substantially identical to RF amplifier device(), and to the extent that various features of device′ are the same as features of device, the same reference numbers are used. For the purpose of brevity, the details of all of the identical features of device′ that are discussed elsewhere in conjunction with device, those details are not repeated here. Instead, it should be understood that the description (and embodiments) of any features of device′ that have identical reference numbers as deviceis incorporated herein to this brief description of device′.

422 423 424 424 425 425 426 426 450 450 421 423 470 470 421 434 434 464 464 424 424 425 425 450 450 470 470 580 580 452 452 450 450 486 486 Specifically, RF amplifier device′ includes a discrete package body, first through fourth amplifier input terminals,′,,′, first and second output terminals,′, first and second carrier amplifier dies,′ coupled to a conductive flangeof the package body, first and second peaking amplifier dies,′ coupled to the conductive flange, and various inductive elements (e.g., wirebonds,′,,′) electrically coupling the input terminals,′,,′ to the carrier and peaking amplifier dies,′,,′. In addition, an output combiner circuit,′ is electrically coupled between the output,′ of each carrier amplifier die,′ and a combining node,′.

580 580 480 480 580 580 527 1 527 1 527 2 527 2 580 580 584 584 484 484 483 483 584 584 485 5 FIG. 4 FIG. 4 FIG. 5 FIG. The output combiner circuits,′ illustrated inare different from the output combiner circuits,′ of. More specifically, each output combiner circuit,′ includes two shunt circuit access terminals-,-′,-,-′, rather than only a single shunt circuit access terminal. Additionally, the output combiner circuits,′ include conductive paths,′ on the transmitter substrate, rather than simple conductive pads (e.g., pads,′,). In the embodiment of, the shunt capacitors,′ are electrically coupled between the conductive paths,′ and the ground referenceof the transmitter substrate.

5 FIG. 481 481 482 482 352 352 452 452 386 386 486 486 527 1 527 1 527 2 527 2 584 584 481 481 482 482 481 481 580 580 352 352 452 452 527 1 527 1 482 482 580 580 472 472 486 486 527 2 527 2 527 1 527 2 527 1 527 2 584 584 584 584 527 1 527 1 527 2 527 2 584 584 580 580 527 1 527 1 527 2 527 2 580 580 580 580 481 481 482 482 527 1 527 1 527 2 527 2 584 584 In, the first and second inductive elements,′,,′ still are coupled in series between the carrier amplifier output,′,,′ and the combining node,′,,′. However, the shunt circuit access terminals-,-′,-,-′ and the conductive path,′ also are connected in series between the first and second inductive elements,′,,′. More specifically, each wirebond,′ corresponding to a first inductive element of the output combiner circuit,′ has a first end coupled to the carrier amplifier output,′,,′, and a second end coupled to a first shunt circuit access terminal-,-′. Further, each wirebond,′ corresponding to a second inductive element of the output combiner circuit,′ has a first end coupled to the peaking amplifier output,′ (i.e., to the combining node,′), and a second end coupled to a second shunt circuit access terminal-,-′. Each pair of shunt circuit access terminals (e.g., a first pair consisting of terminals-and-, and a second pair consisting of terminals-′ and-′) is electrically coupled through one of the conductive paths,′ on the transmitter substrate. Because each of the conductive paths,′ have an electrical length between the first terminals-,-′ and the second terminals-,-′, each of the conductive paths,′ contribute to the total electrical length through the output combiner circuits,′. Additionally, the shunt circuit access terminals-,-′,-,-′ also contribute a small amount of electrical length to the total electrical length through the output combiner circuits,′. According to one or more embodiments, within each output combiner circuit,′, the total electrical length of the first and second inductive elements,′,,′, the shunt circuit access terminals-,-′,-,-′, and the conductive path,′ is about 90 degrees (i.e., exactly 90 degrees or between about 85 and 95 degrees).

322 422 422 383 383 483 483 316 316 416 416 383 383 483 483 380 380 480 480 316 316 416 416 383 383 483 483 380 380 480 480 316 316 416 416 Regardless of the number of shunt circuit access terminals included in the device,,′, the capacitance value of each shunt capacitor,′,,′ may be selected to “tune” each Doherty power amplifier,′,,′ for optimal performance within a particular operational frequency band. In other words, when the shunt capacitor,′,,′ has a first capacitance value, inclusion of that capacitor in an output combiner circuit,′,′,′ may tune the Doherty power amplifier,′,,′ for optimal performance within a first operational frequency band (e.g., 1805-1880 MHz). Conversely, when the shunt capacitor,′,,′ has a second capacitance value, inclusion of that capacitor in the output combiner circuit,′,′,′ may tune the Doherty power amplifier,′,,′ for optimal performance within a second and different operational frequency band (e.g., 2110-2170 MHz).

383 383 483 483 316 316 416 416 383 383 483 483 301 401 322 422 383 383 483 483 322 422 108 101 201 301 401 110 210 310 410 383 383 483 483 101 201 301 401 1 FIG. As indicated above the shunt capacitors,′,,′ are part of the “external circuitry” of each Doherty power amplifier,′,,′, In other words, the shunt capacitors,′,,′ are physically coupled to the transmitter substrate,, and are not integrated within the devices,. Externalizing the shunt capacitors,′,,′ has the advantageous effect of enabling identical packaged amplifier devices,to be used in multiple transmitters (e.g., transmitters,), even when the multiple transmitters are intended for operation at different operational frequencies. In addition, the multiple transmitters all may have the same layout on a transmitter substrate,,,. All that is needed to optimize a particular amplification stage,,,for operation at a particular frequency is to attach a shunt capacitor,′,,′ with a capacitance value selected for that frequency to the transmitter substrate,,,.

360 360 320 320 386 386 486 486 380 380 480 480 360 320 320 370 370 470 470 370 370 470 470 360 360 301 401 320 320 325 325 425 425 325 325 425 425 322 422 364 364 464 464 322 422 325 325 425 425 370 370 The peaking amplification path,′ is coupled between the second splitter output,′ and the combining node,′,,′ of the output combiner circuit,′,,′. Each peaking amplification path, 360′includes a series of conductive elements between the second splitter output,′ and the peaking amplifier,′,,′, and the peaking amplifier,′,,′. The series of conductive elements of the peaking amplification path,′ includes: 1) a conductive trace (not numbered) on the transmitter substrate,between the second splitter output,′ and the second or fourth amplifier input terminals,′,,′; 2) one of the second or fourth amplifier input terminals,′,,′ of the device,; and 3) an inductive element,′ (e.g., one or more wirebonds,′) within the device,between the second or fourth amplifier input terminal,′,,′ and the peaking amplifier,′.

325 325 425 425 301 401 364 364 464 464 325 325 425 425 371 371 471 471 370 370 470 470 364 364 464 464 325 325 425 425 371 371 471 471 370 370 470 470 364 364 464 464 362 362 362 362 362 362 364 364 464 464 4 FIG. Distal ends of the second and fourth amplifier input terminals,′,,′ are coupled (e.g., soldered) to ends of the conductive traces (or to conductive pads) on the transmitter substrate,. Each inductive element,′,,′ provides an electrical connection between one of the second and fourth amplifier input terminals,′,,′ and an input,′,,′ to the peaking amplifier,′,,′. As shown in, each inductive element,′ may be implemented as one or more wirebonds,′ between the second or fourth amplifier input terminals,′,,′ and the input,′,,′ to the peaking amplifier,′,,′. In addition, the inductive element,′,,′ may form a portion of an optional peaking IMN,′. When included, the peaking IMN,′ is configured to incrementally increase the circuit impedance. For example, but not by way of limitation, the peaking IMN,′ may include, for example, a lowpass or bandpass circuit configured as a T- or pi-impedance matching network, where the inductive element,′,,′ provides a series inductance in the circuit.

370 370 470 470 421 323 423 370 370 470 470 371 371 471 471 371 371 471 471 364 364 464 464 362 362 325 325 370 370 470 470 372 372 472 472 370 370 470 470 370 370 470 470 421 As mentioned above, each peaking amplifier,′ may be implemented as a power transistor in a peaking amplifier die,′, which is physically and electrically coupled to the conductive flangeof the package body,. As used herein, “peaking amplifier” and “peaking amplifier die” may be used interchangeably. Each peaking amplifier,′,,′ has a peaking amplifier input,′,,′ (e.g., a gate terminal) and two current-carrying terminals (e.g., drain and source terminals). As indicated above, the peaking amplifier input,′,,′ is coupled through inductive element,′,,′ (and/or through the peaking IMN,′) to the second or fourth amplifier input terminal,′. One of the current-carrying terminals (e.g., the drain terminal) of the peaking amplifier,′,,′ functions as a peaking amplifier output,′,,′, at which an amplified peaking signal is produced by the peaking amplifier,′,,′. The other current-carrying terminal (e.g., the source terminal) of the peaking amplifier,′,,′ may be coupled to a ground reference node (e.g., to the conductive flange).

370 370 470 470 371 371 471 471 372 372 472 472 372 372 472 472 386 386 486 486 380 380 480 480 372 372 472 472 386 386 486 486 370 370 470 470 372 372 472 472 386 386 486 486 The peaking amplifier,′,,′ is configured to amplify the peaking input RF signal received at the peaking amplifier input,′,,′, and to produce an amplified peaking signal at the peaking amplifier output,′,,′. As mentioned previously, the peaking amplifier output,′,,′ may be co-located with the combining node,′,,′ of the output combiner circuit,′,,′. For example, the peaking amplifier output,′,,′ and the combining node,′,,′ may be a same conductive feature (e.g., a drain terminal of the peaking amplifier,′,,′). Accordingly, an electrical distance between the peaking amplifier output,′,,′ and the combining node,′,,′ may be about zero degrees.

386 386 486 486 316 316 416 416 356 356 456 456 386 386 486 486 326 326 426 426 356 356 456 456 386 386 486 486 326 326 426 426 Each combining node,′,,′ is configured to combine the amplified carrier signal and the amplified carrier signal received at that node, in order to produce an amplified output signal for each Doherty power amplifier,′,,′. According to one or more embodiments, inductive element,′,,′ is electrically connected between the combining node,′,,′ and the first or second output terminal,′,,′. For example, the inductive element,′ may be implemented as one or more wirebonds,′ between the combining node,′,,′ and the first or second output terminal,′,,′.

326 326 426 426 388 488 Once an amplified output signal is produced at each of the first and second output terminals,′,,′, those output signals are combined by the signal combiner,, as discussed above in detail.

4 FIG. 428 428 429 429 351 351 371 371 451 451 471 471 350 350 370 370 450 450 470 470 431 431 351 351 371 371 451 451 471 471 350 350 370 370 450 450 470 470 428 428 429 429 431 431 316 316 416 416 310 410 310 410 350 350 450 450 370 370 470 470 As a side note, and as illustrated in, first and second DC bias circuits,′,,′ are coupled to the inputs,′,,′,,′,,′ (e.g., gate terminals) of the carrier and peaking amplifiers,′,,′,,′,,′. Further, third DC bias circuits,′ are coupled to the outputs,′,,′,,′,,′ (e.g., drain terminals) of the carrier and peaking amplifiers,′,,′,,′,,′. These DC bias circuits,′,,′,,′ convey gate and drain DC bias voltages, respectively, that will ensure proper operation of the Doherty power amplifiers,′,,′ within the amplification stage,. More specifically, during operation of the amplification stage,, each of the carrier amplifiers,′,,′ may be biased to operate in class AB mode or deep class AB mode, and each of the peaking amplifiers,′,,′ may be biased to operate in class C mode or deep class C mode.

316 316 416 416 370 370 470 470 316 316 416 416 350 350 450 450 370 370 470 470 370 370 470 470 350 350 450 450 317 317 417 417 330 330 360 360 350 350 370 370 450 450 470 470 At low to moderate input signal power levels (i.e., where the power of an input signals at the input to the first or second Doherty power amplifier,′,,′ is lower than the turn-on threshold level of the associated peaking amplifier,′,,′), the Doherty power amplifier,′,,′ operates in a low-power mode in which the carrier amplifier,′,,′ operates to amplify the input signal, and the peaking amplifier,′,,′ is minimally conducting (e.g., the peaking amplifier,′,,′ essentially is in an off state). Conversely, as the input signal power increases to a level at which the carrier amplifier,′,,′ reaches voltage saturation, the signal splitter,′,,′ divides the energy of the input signal between the carrier and peaking amplifier paths,′,,′, and both amplifiers,′,,′,,′,,′ operate to amplify their respective portion of the input signal.

350 350 450 450 370 370 470 470 326 326 426 426 350 350 450 450 370 370 470 470 350 350 450 450 380 380 480 480 350 350 450 450 326 326 426 426 As the input signal level increases beyond the point at which the carrier amplifier,′,,′ is operating in compression, the peaking amplifier,′,,′ conduction also increases, thus supplying more current to output terminal,′,,′. In response, the load line impedance of the carrier amplifier output decreases. In fact, an impedance modulation effect occurs in which the load line of the carrier amplifier,′,,′ changes dynamically in response to the input signal power (i.e., the peaking amplifier,′,,′ provides active load pulling to the carrier amplifier,′,,′). The output combiner circuit,′,,′, transforms the carrier amplifier load line impedance to a high value at backoff, allowing the carrier amplifier,′,,′ to efficiently supply power to the output terminal,′,,′ over an extended output power range.

310 410 380 380 480 480 580 580 350 450 386 386 486 486 370 470 386 386 486 486 35 FIG. 3 5 FIGS.- 3 4 FIGS., 3 5 FIGS.- 3 5 FIGS.- 3 5 FIGS.- The embodiments of amplification stages,discussed in conjunction withcorrespond to physical implementations of dual 90/0 Doherty power amplifiers, as discusses above. As a reminder, a 90/0 Doherty power amplifier has an output combining circuit (e.g., circuits,′,,′,,′,) in which an electrical length between the output of a first amplifier or amplifier die (e.g., amplifieror amplifier die,) and a combining node (e.g., combining node,′,,′,) is about 90 degrees, and in which an electrical length between the output of a second amplifier or amplifier die (e.g., amplifieror amplifier die,) and a combining node (e.g., combining node,′,,′,) is about zero degrees.

According to one or more other embodiments, an amplification stage may include one or more Doherty power amplifiers, each with an output combining circuit in which an electrical length between the output of a first amplifier or amplifier die and a combining node is about 90 degrees, and in which an electrical length between the output of a second amplifier or amplifier die and a combining node is about 180 degrees. Such a Doherty power amplifier is referred to as a “90/180 Doherty power amplifier.”

6 FIG. 1 2 FIGS., 6 FIG. 7 FIG. 6 FIG. 610 110 210 710 is a schematic drawing of an amplification stage(e.g., amplification stage,,) that includes a dual 90/180 Doherty power amplifier with tunable output combiner circuits, in accordance with an example embodiment. For enhanced understanding,should be viewed simultaneously with, which is a top view of a physical implementation of an amplification stagethat includes the dual 90/180 Doherty power amplifier of.

680 680 780 780 650 750 686 686 786 786 90 670 770 686 686 786 786 6 7 FIGS., 6 7 FIGS., 6 7 FIGS., 6 7 FIGS., 6 7 FIGS., Again, some terminology may be useful at this point. In particular, the term “90/180 Doherty power amplifier” means a Doherty power amplifier that has an output combining circuit (e.g., circuits,′,,′,) in which an electrical length between the output of one amplifier or amplifier die (e.g., amplifieror amplifier die,) and a combining node (e.g., combining node,′,,′,) is aboutdegrees (i.e., exactly 90 degrees or between about 85 and 95 degrees), and in which an electrical length between the output of another amplifier or amplifier die (e.g., amplifieror amplifier die,) and a combining node (e.g., combining node,′,,′,) is about 180 degrees (e.g., exactly 180 degrees or between about 170 and 190 degrees).

610 710 301 401 616 716 616 716 610 710 311 411 312 412 616 716 616 716 388 488 392 492 The amplification stage,essentially includes a dual 90/180 Doherty power amplifier coupled to the transmitter substrate,, which includes a first Doherty power amplifier,and a second Doherty power amplifier′,′ arranged in parallel. More particularly, amplification stage,includes a transmitter input terminal,, a first signal power splitter,, the first Doherty power amplifier,, the second Doherty power amplifier′,′, a signal power combiner,, and a transmitter output terminal,.

310 410 610 710 310 410 610 710 301 401 311 411 312 317 317 412 417 417 301 401 311 411 312 317 317 412 417 417 3 4 FIGS.and The “external circuitry” of RF amplifier stages,may be similar or identical to the “external circuitry” of RF amplifier stages,. More specifically, as with RF amplifier stages,, RF amplifier stages,also include a transmitter substrate,, an RF input,, and first, second, and third signal splitters,,′,,,′ mounted on the transmitter substrate,. The RF input,and the first, second, and third signal splitters,,′,,,′ all may be electrically coupled together as described previously in conjunction with.

310 410 610 710 319 319 320 320 317 317 417 417 624 624 625 625 724 724 725 725 624 624 625 625 724 724 725 725 324 324 325 325 424 424 425 425 310 410 610 710 388 488 301 401 326 326 426 426 622 722 389 390 388 488 310 410 610 710 383 383 301 401 484 484 327 327 427 427 622 722 610 710 3 4 FIGS., 3 4 FIGS.and 6 7 FIGS.and In addition, as with RF amplifier stages,, the external circuitry of RF amplifier stages,also includes various conductive traces that electrically connect the various outputs,′,,′ of the second and third signal splitters,′,,′ with amplifier input terminals,′,,′,,′,,′. The amplifier input terminals,′,,′,,′,,′ have the same physical and electrical characteristics as the amplifier input terminals,′,,′,,′,,′ (). Further, as with RF amplifier stages,, the external circuitry of RF amplifier stages,also includes a signal combiner,on the transmitter substrate,, and additional conductive traces that electrically connect first and second amplifier output terminals,′,′ of device,to inputs,of the signal combiner,. Further still, as with RF amplifier stages,, the external circuitry of RF amplifier stages,also includes shunt capacitors,′ on the transmitter substrate,, which are coupled (e.g., through conductive pads,′) to shunt circuit access terminals,′,,′ of device,. The details of the external circuitry associated with RF amplifier stages,will not be repeated here, for brevity, but instead the description of the details of the identical circuitry discussed previously in conjunction withis incorporated into this description of.

622 722 322 422 622 722 322 422 622 722 322 422 622 722 322 422 622 722 650 650 750 750 350 350 450 450 670 670 770 770 370 370 470 470 3 4 FIGS., 3 4 FIGS., 3 4 FIGS., 3 4 FIGS.and 6 7 FIGS.and In addition, RF amplifier devices,are substantially similar to RF amplifier devices,(), and to the extent that various features of devices,are the same as features of devices,, the same reference numbers are used. For the purpose of brevity, the details of all of the identical features of devices,that are discussed elsewhere in conjunction with devices,, those details are not repeated here. Instead, it should be understood that the description (and embodiments) of any features of devices,that have identical reference numbers as devices,is incorporated herein to this brief description of devices,. It should be noted also that carrier amplifiers (and amplifier dies),′,,′ are the same as carrier amplifiers (and amplifier dies),′,,′ (), peaking amplifiers,′,,′ are the same as peaking amplifiers,′,,′ (), and all details associated with the carrier and peaking amplifiers (and amplifier dies) discussed above in conjunction withare incorporated into this description of the carrier and peaking amplifiers (and amplifier dies) of.

622 722 423 624 624 625 625 724 724 725 725 326 326 426 426 327 327 427 427 650 650 750 750 421 423 670 670 770 770 421 Specifically, RF amplifier devices,includes a discrete package body, first through fourth amplifier input terminals,′,,′,,′,,′, first and second output terminals,′,,′, first and second shunt circuit access terminals,′,,′, first and second carrier amplifiers (amplifier dies),′,,′ coupled to a conductive flangeof the package body, and first and second peaking amplifiers (amplifier dies),′,,′ coupled to the conductive flange.

6 7 FIGS.and 632 632 662 662 732 732 762 762 624 624 625 625 724 724 725 725 650 650 670 670 750 750 770 770 632 632 662 662 732 732 762 762 635 635 665 665 735 735 765 765 421 735 735 765 765 632 632 662 662 732 732 762 762 624 624 625 625 724 650 650 670 670 750 750 770 770 In the embodiment of, input matching networks (IMNs),′,,′,,′,,′ are electrically coupled between the input terminals,′,,′,,′,,′ and the carrier and peaking amplifiers (amplifier dies),′,,′,,′,,′. According to one or more embodiments, the IMNs,′,,′,,′,,′ each include an integrated passive device,′,,′,,′,,′ coupled to the conductive flange, where the integrated passive device,′,,′ includes a shunt capacitor and possibly other circuitry. Each IMN,′,,′,,′,,′ also includes first and second inductive elements (e.g., wirebonds) coupled in series between the amplifier input terminals,′,,′,, 724′, 725, 725′ and the carrier and peaking amplifiers (amplifier dies),′,,′,,′,,′.

622 722 322 422 610 710 680 680 780 780 380 380 480 480 6 7 FIGS.and 3 4 FIGS.and The differences between RF amplifier devices,and RF amplifier devices,will now be discussed in detail. Specifically, because amplifier stage,includes 90/180 Doherty power amplifiers (rather than 90/0 Doherty power amplifiers), the output combiner circuits,′,,′ illustrated inare different from the output combiner circuits,′,,′ of.

6 7 FIGS.and 652 652 672 672 752 752 772 772 650 650 750 750 670 670 770 770 680 680 780 780 680 680 780 780 672 672 772 772 680 680 780 780 652 652 752 752 Referring to, the outputs,′,,′,,′,,′ (e.g., drain terminals) of both the carrier amplifier,′,,′ and the peaking amplifier,′,,′ are electrically coupled to an output combiner circuit,′,,′. The output combiner circuit,′,,′ is configured to provide an impedance inversion, and also to impart a phase shift to the amplified peaking signal produced at the peaking amplifier output,′,,′. In addition, the output combiner circuit,′,,′ also is configured to impart a phase shift to the amplified carrier signal produced at the carrier amplifier output,′,,′.

680 680 780 780 656 656 756 756 681 681 682 682 781 781 782 782 383 383 483 483 686 686 786 786 686 686 786 786 326 326 426 426 According to one or more embodiments, each output combiner circuit,′,,′ includes a first inductive element,′ (e.g., one or more first wirebonds,′), second and third, series-connected inductive elements,′,,′ (e.g., one or more second wirebonds,′ and one or more third wirebonds,′), a shunt capacitor,′,,′, and a combining node,′,,′. As will be discussed in more detail later, the combining node,′,,′ may be co-located with the first and second output terminals,′,,′.

656 656 756 756 652 652 752 752 686 686 786 786 326 326 426 426 656 656 756 756 652 652 752 752 326 326 426 426 686 686 786 786 656 656 756 756 656 656 756 756 652 652 752 752 686 686 786 786 According to one or more embodiments, the first inductive element,′,,′ is electrically coupled between the carrier amplifier output,′,,′ and the combining node,′,,′ (e.g., the first or second output terminal,′,,′). For example, each first inductive element,′ may be implemented as a first set of wirebonds,′, where each wirebond has a first end coupled to the carrier amplifier output,′,,′, and a second end coupled to the first or second output terminal,′,,′ (e.g., the combining node,′,,′). According to one or more embodiments, the electrical length of the first inductive element,′,,′ is about 90 degrees (i.e., exactly 90 degrees or between about 85 and 95 degrees). Accordingly, the first inductive element,′,,′ imparts about 90 degrees of phase delay to the amplified carrier signal between the carrier amplifier output,′,,′ and the combining node,′,,′.

681 681 682 682 781 781 782 782 672 672 772 772 686 686 786 786 327 327 427 427 681 681 682 682 781 781 782 782 681 681 781 781 672 672 772 772 327 327 427 427 682 682 782 782 327 327 427 427 686 686 786 786 326 326 426 426 681 681 682 682 The second and third inductive elements,′,,′,,′,,′ are coupled in series between the peaking amplifier output,′,,′ and the combining node,′,,′, with an intermediate node (corresponding to shunt circuit access terminals,′,,′) between each series-connected set of second and third inductive elements,′,,′,,′,,′. For example, each second inductive element,′ may be implemented as a second set of wirebonds,′, where each wirebond has a first end coupled to the peaking amplifier output,′,,′, and a second end coupled to the shunt circuit access terminal,′,,′. Each third inductive element,′ may be implemented as a third set of wirebonds,′, where each wirebond has a first end coupled to the shunt circuit access terminal,′,,′, and a second end coupled to the combining node,′,,′ (e.g., to the first or second output terminal,′,,′). In alternate embodiments, the second and third inductive elements,′,,′ may be implemented using conductive traces, rather than wirebonds.

681 681 682 682 781 781 782 782 681 681 682 682 781 781 782 782 672 672 772 772 686 686 786 786 According to one or more embodiments, the total electrical length of the second and third inductive elements,′,,′,,′,,′ is about 180 degrees (i.e., exactly 180 degrees or between about 170 and 190 degrees). Accordingly, the second and third inductive elements,′,,′,,′,,′ impart about 180 degrees of phase delay to the amplified peaking signal between the peaking amplifier output,′,,′ and the combining node,′,,′.

7 FIG. 1 FIG. 427 427 484 484 301 401 383 383 483 483 301 401 484 484 485 301 401 383 383 483 483 484 484 485 301 401 383 383 483 483 616 616 716 716 383 383 483 483 622 722 108 101 201 301 401 610 710 383 383 483 483 101 201 301 401 As best shown in, each shunt circuit access terminal,′ (or “intermediate node”) is coupled to a conductive pad,′ on the transmitter substrate,. Further, according to one or more further embodiments, a shunt capacitor,′,,′ is coupled to the transmitter substrate,between the conductive pad,′ and a ground referenceof the transmitter substrate,. More specifically, each shunt capacitor,′,,′ may have a first terminal connected to the conductive pad,′, and a second terminal coupled to a ground referenceof the transmitter substrate,. Once again, the capacitance value of each shunt capacitor,′,,′ may be selected to “tune” each Doherty power amplifier,′,,′ for optimal performance at a particular operational frequency. Additionally, as discussed above, externalizing the shunt capacitors,′,,′ has the advantageous effect of enabling identical packaged amplifier devices,to be used in multiple transmitters (e.g., transmitters,), even when the multiple transmitters are intended for operation at different operational frequencies. In addition, the multiple transmitters all may have the same layout on a transmitter substrate,,,. All that is needed to optimize a particular amplification stage,for operation at a particular frequency is to attach a shunt capacitor,′,,′ with a capacitance value selected for that frequency to the transmitter substrate,,,.

An embodiment of an RF amplifier includes a discrete package body, and a first signal output terminal, a second signal output terminal, one or more first shunt circuit access terminals, and one or more second shunt circuit access terminals connected to the discrete package body. First, second, third, and fourth power amplifiers also are connected to the discrete package body. The first power amplifier also includes a first amplifier output, which is electrically coupled through a first inductive element to the first signal output terminal and is electrically coupled through a second inductive element to the one or more first shunt circuit access terminals. The second power amplifier also includes a second amplifier output, which is electrically coupled through a third inductive element to the one or more first shunt circuit access terminals. The third power amplifier includes a third amplifier output, which is electrically coupled through a fourth inductive element to the second signal output terminal and is electrically coupled through a fifth inductive element to the one or more second shunt circuit access terminals. The fourth power amplifier includes a fourth amplifier output, which is electrically coupled through a sixth inductive element to the one or more second shunt circuit access terminals. The RF amplifier also includes a first output combiner circuit that includes the second and third inductive elements, and a second output combiner circuit that includes the fifth and sixth inductive elements.

According to a further embodiment, the first amplifier output corresponds to a first combining node of the first output combiner circuit, and a first electrical length between the first amplifier output and the second amplifier output through the second and third inductive elements is about 90 degrees.

According to another further embodiment, the first signal output terminal corresponds to a first combining node of the first output combiner circuit, the one or more first shunt circuit access terminals consists of a single first shunt circuit access terminal, the second amplifier output is electrically connected through the third inductive element to the to the single first shunt circuit access terminal, and the second inductive element has a first end connected to the first signal output terminal and a second end connected to the single first shunt circuit access terminal. In such an embodiment, a first electrical length between the second amplifier output and the first signal output terminal through the second and third inductive elements is about 180 degrees, and a second electrical length between the first amplifier output and the first signal output terminal through the first inductive element is about 90 degrees.

Another embodiment of an RF amplifier device includes a discrete package body, and a first signal output terminal, a first shunt circuit access terminal, and first and second power amplifiers connected to the discrete package body. The first power amplifier includes a first amplifier output electrically coupled through a first inductive element to the first signal output terminal. A second inductive element has a first end coupled to the first signal output terminal and a second end coupled to the first shunt circuit access terminal. The second power amplifier includes a second amplifier output electrically coupled through a third inductive element to the first shunt circuit access terminal. A first output combiner circuit includes the first, second, and third inductive elements, where the first signal output terminal corresponds to a first combining node of the first output combiner circuit.

According to a further embodiment, a first electrical length between the second amplifier output and the first signal output terminal through the second and third inductive elements is about 180 degrees, and a second electrical length between the first amplifier output and the first signal output terminal through the first inductive element is about 90 degrees.

An embodiment of an RF transmitter includes a transmitter substrate and an amplifier coupled to the transmitter substrate. The amplifier includes a transmitter input terminal, a transmitter output terminal, and the radio frequency amplifier device of the previous paragraph, which is physically coupled to the transmitter substrate. The radio frequency amplifier device also includes one or more first amplifier input terminals and one or more second amplifier input terminals. A first signal power splitter is physically coupled to the transmitter substrate and has a first splitter input terminal, a first splitter output terminal, and a second splitter output terminal. The first splitter input terminal is electrically coupled to the transmitter input terminal, the first splitter output terminal is electrically coupled to the one or more first amplifier input terminals, and the second splitter output terminal is electrically coupled to the one or more second amplifier input terminals. A first capacitor is physically coupled to the first transmitter substrate and has a first capacitor terminal coupled to the one or more first shunt circuit access terminals and a second capacitor terminal coupled to a ground reference of the transmitter substrate. A second capacitor is physically coupled to the transmitter substrate and has a third capacitor terminal coupled to the one or more second shunt circuit access terminals and a fourth capacitor terminal coupled to the ground reference of the first transmitter substrate. The RF transmitter also includes a signal power combiner physically coupled to the transmitter substrate, which has a first combiner input terminal, a second combiner input terminal, and a combiner output terminal. The first combiner input terminal is electrically coupled to the first signal output terminal, and the second combiner input terminal is electrically coupled to the second signal output terminal.

The connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the subject matter. In addition, certain terminology may also be used herein for the purpose of reference only, and thus are not intended to be limiting, and the terms “first,” “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context.

As used herein, a “node” means any internal or external reference point, connection point, junction, signal line, conductive element, or the like, at which a given signal, logic level, voltage, data pattern, current, or quantity is present. Furthermore, two or more nodes may be realized by one physical element (and two or more signals can be multiplexed, modulated, or otherwise distinguished even though received or output at a common node).

The foregoing description refers to elements or nodes or features being “connected” or “coupled” together. As used herein, unless expressly stated otherwise, “connected” means that one element is directly joined to (or directly communicates with) another element, and not necessarily mechanically. Likewise, unless expressly stated otherwise, “coupled” means that one element is directly or indirectly joined to (or directly or indirectly communicates with, electrically or otherwise) another element, and not necessarily mechanically. Thus, although the schematic shown in the figures depict one exemplary arrangement of elements, additional intervening elements, devices, features, or components may be present in an embodiment of the depicted subject matter.

As used herein, the words “exemplary” and “example” mean “serving as an example, instance, or illustration.” Any implementation described herein as exemplary or an example is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, or detailed description.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.